Incidence of Recurrent Exertional Heat Stroke in a Warm-Weather Road Race.

Background and Objectives: Exertional heat stroke (EHS) survivors may be more susceptible to subsequent EHS; however, the occurrence of survivors with subsequent EHS episodes is limited. Therefore, the purpose of this study was to evaluate the incidence of participants with repeated EHS (EHS-2+) cases in a warm-weather road race across participation years compared to those who experienced 1 EHS (EHS-1). Materials and Methods: A retrospective observational case series design was utilized. Medical record data from 17-years at the Falmouth Road Race between 2003-2019 were examined for EHS cases. Incidence of EHS-2+ cases per race and average EHS cases per EHS-2+ participant were calculated (mean ± SD) and descriptive factors (rectal temperature (TRE), finish time (FT), Wet Bulb Globe Temperature (WBGT), age, race year) for each EHS was collected. Results: A total of 333 EHS patients from 174,853 finishers were identified. Sixteen EHS-2+ participants (11 males, 5 females, age = 39 ± 16 year) accounted for 11% of the total EHS cases (n = 37/333). EHS-2+ participants had an average of 2.3 EHS cases per person (range = 2-4) and had an incidence rate of 2.6 EHS per 10 races. EHS-2+ participants finished 93 races following initial EHS, with 72 of the races (77%) completed without EHS incident. Initial EHS TRE was not statistically different than subsequent EHS initial TRE (+0.3 ± 0.9 °C, p > 0.050). Initial EHS-2+ participant FT was not statistically different than subsequent EHS FT (-4.2 ± 7.0 min, p > 0.050). The years between first and second EHS was 3.6 ± 3.5 year (Mode: 1, Range: 1-12). Relative risk ratios revealed that EHS patients were at a significantly elevated risk for subsequent EHS episodes 2 years following their initial EHS (relative risk ratio = 3.32, p = 0.050); however, the risk from 3-5 years post initial EHS was not statistically elevated, though the relative risk ratio values remained above 1.26. Conclusions: These results demonstrate that 11% of all EHS cases at the Falmouth Road Race are EHS-2+ cases and that future risk for a second EHS episode at this race is most likely to occur within the first 2 years following the initial EHS incident. After this initial 2-year period, risk for another EHS episode is not significantly elevated. Future research should examine factors to explain individuals who are susceptible to multiple EHS cases, incidence at other races and corresponding prevention strategies both before and after initial EHS.

Age- and Sex-Based Differences in Exertional Heat Stroke Incidence in a 7-Mile Road Race.

CONTEXT: Sex, age, and wet-bulb globe temperature (WBGT) have been proposed risk factors for exertional heat stroke (EHS) despite conflicting laboratory and epidemiologic evidence. OBJECTIVE: To examine differences in EHS incidence while accounting for sex, age, and environmental conditions. DESIGN: Observational study. SETTING: Falmouth Road Race, a warm-weather 7-mi (11.26-km) running road race. PATIENTS OR OTHER PARTICIPANTS: We reviewed records from patients treated for EHS at medical tents. MAIN OUTCOME MEASURE(S): The relative risk (RR) of EHS between sexes and across ages was assessed with males as the reference population. Multivariate linear regression analyses were calculated to determine the relative contribution of sex, age, and WBGT to the incidence of EHS. RESULTS: Among 343 EHS cases, the female risk of EHS was lower overall (RR = 0.71; 95% confidence interval [CI] = 0.58, 0.89; P = .002) and for age groups 40 to 49 years (RR = 0.43; 95% CI = 0.24, 0.77; P = .005) and 50 to 59 years (RR = 0.31; 95% CI = 0.13, 0.72; P = .005). The incidence of EHS did not differ between sexes in relation to WBGT (P > .05). When sex, age, and WBGT were considered in combination, only age groups <14 years (ß = 2.41, P = .008), 15 to 18 years (ß = 3.83, P < .001), and 19 to 39 years (ß = 2.24, P = .014) significantly accounted for the variance in the incidence of EHS (R2 = .10, P = .006). CONCLUSIONS: In this unique investigation of EHS incidence in a road race, we found a 29% decreased EHS risk in females compared with males. However, when sex was considered with age and WBGT, only younger age accounted for an increased incidence of EHS. These results suggest that road race medical organizers should consider participant demographics when organizing the personnel and resources needed to treat patients with EHS. Specifically, organizers of events with greater numbers of young runners (aged 19 to 39 years) and males should prioritize ensuring that medical personnel are adequately prepared to handle patients with EHS.

Menstrual cycle and thermoregulation during exercise in the heat: A systematic review and meta-analysis.

Research conducted on exercise in the heat has been largely conducted in males, leaving women understudied. Of research including women, results are inconsistent on the impact of menstrual cycle phase on thermoregulation. OBJECTIVES: The purpose of this systematic review is to quantify published investigations in thermal physiology that include menstrual cycle comparisons and assess aggregate data of investigations that include menstrual cycle variation and aerobic exercise in the heat. METHODS: 367 research articles were identified via systematic review and inclusion criteria and yielded 9 papers included in this analysis for a total number of 83 research subjects. Effect size estimates (Hedge's g) were utilized for initial (pre-exercise) and post-exercise internal body temperature (rectal or esophageal, Tint), sweat rate, mean skin temperature, and exercise heart rate. RESULTS: Pooled effect size showed significantly greater initial Tint (1.231±0.186, p<0.01) and post-exercise Tint (0.455±0.153, p<0.01) in the luteal compared to follicular phases. No significant differences were present in mean skin temperature, sweat rate, or exercise heart rate across menstrual phases in analyses of aggregate data. CONCLUSIONS: The limited available data suggest that observed increases in initial Tint in the luteal phase are maintained throughout and post-exercise without an observed impact in sweat rate or mean skin temperature.

Exertional heat illness incidence and on-site medical team preparedness in warm weather.

To investigate the influence of estimated wet bulb globe temperature (WBGT) and the International Institute of Race Medicine (IIRM) activity modification guidelines on the incidence of exertional heat stroke (EHS) and heat exhaustion (HEx) and the ability of an on-site medical team to treat those afflicted. Medical records of EHS and HEx patients over a 17-year period from the New Balance Falmouth Road Race were examined. Climatologic data from nearby weather stations were obtained to calculate WBGT with the Australian Bureau of Meteorology (WBGTA) and Liljegren (WBGTL) models. Incidence rate (IR) of EHS, HEx, and combined total of EHS and HEx (COM) were calculated, and linear regression analyses were performed to assess the relationship between IR and WBGTA or WBGTL. One-way ANOVA was performed to compare differences in EHS, HEx, and COM incidence to four alert levels in the IIRM guidelines. Incidence of EHS, HEx, and COM was 2.12, 0.98, and 3.10 cases per 1000 finishers. WBGTA explained 48, 4, and 46% of the variance in EHS, HEx, and COM IR; WBGTL explained 63, 13, and 69% of the variance in EHS, HEx, and COM IR. Main effect of WBGTA and WBGTL on the alert levels were observed in EHS and COM IR (p < 0.05). The cumulative number of EHS patients treated did not exceed the number of cold water immersion tubs available to treat them. EHS IR increased as WBGT and IIRM alert level increased, indicating the need for appropriate risk mitigation strategies and on-site medical treatment.

Top 10 Research Questions Related to Preventing Sudden Death in Sport and Physical Activity.

Participation in organized sport and recreational activities presents an innate risk for serious morbidity and mortality. Although death during sport or physical activity has many causes, advancements in sports medicine and evidence-based standards of care have allowed clinicians to prevent, recognize, and treat potentially fatal injuries more effectively. With the continual progress of research and technology, current standards of care are evolving to enhance patient outcomes. In this article, we provided 10 key questions related to the leading causes and treatment of sudden death in sport and physical activity, where future research will support safer participation for athletes and recreational enthusiasts. The current evidence indicates that most deaths can be avoided when proper strategies are in place to prevent occurrence or provide optimal care.